1. Field of the Invention
The present invention relates to high precision workpiece positioning equipment and, more particularly, to equipment for precisely positioning workpieces in a vertical direction.
2. Description of the Related Art
There are many devices intended to provide physical placement of objects along and around multiple axes. However, with modem advances in technology, the need to precisely position workpieces, such as during manufacturing and testing procedures, has become more prevalent. For example, often, mechanical, optical, electronic, genetic, medical and chemical disciplines require exact placement of various components combined with an ability to manipulate the object in one or more dimensions. Possibly one of the more prominent needs is in the optical world of precision optics, lasers, lenses, and fiber optics. Other needs include micromachining and semiconductor device inspection.
Conventional methods include a series of adjustable leadscrews which are attached to a working platform or table at one end and some suitable base on the other. Each axis may then be manipulated by turning a micrometer type positioner a prescribed amount which, in turn, moves the working platform or table to the desired position relative to its base or some other reference such as an optical axis. However, these types of devices are inherently less precise than the precision required by today's technology.
Other conventional workpiece positioning devices are known to include two wedge-shaped members wherein a first wedge is driven by a leadscrew and is caused to engage the surface of a second wedge connected to the working platform. Thus, as the surfaces of the two wedges and the first wedge is driven forward and backward, the working platform is raised and lowered accordingly. However, conventional wedge-drive workpiece positioning devices exhibit limited ability to precisely position the workpiece, due to the tolerances in the angle, accumulation of manufacturing tolerances and smoothness of the contact surfaces of the opposing wedges.
Another problem with conventional wedge drive designs is a loss of accuracy associated with inadequate stability of the working platform as it is driven along the vertical axis, due, in large part, to the horizontal component of the force exerted by the wedge drive on an elevator component which supports and lifts the working platform. Conventional wedge drive positioning systems typically feature widely spaced cross roller guides which have a certain level of geometry error in the guide planes due to manufacturability. Since there are 3.times.2 surface planes involved, such widely spaced locating surfaces cannot be machined to the exceedingly close tolerances required to achieve the accuracies obtainable with the present invention. The design of the present invention reduces to 2 planes at close proximity.
What is clearly needed is a workpiece positioning device which overcomes the accuracy problems associated with prior art devices and is capable of positioning workpieces with a high degree of precision to meet the needs of present day technology.